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Direct measurements – PASCO TD-8564 THERMAL EFFICIENCY APPARATUS User Manual

Page 9

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012-05443A

Thermal Efficiency Apparatus

5

by using the chart located on the front of the Thermal
Efficiency Apparatus and in Table 1. Notice that as the
temperature increases, the thermistor resistance decreases
(100 k

is a higher temperature than 200 k

).

NOTE: To get the exact temperature reading
the user must interpolate between numbers on the
chart. For example, suppose the ohmmeter reads
118.7 k

. This reading lies between

120 k

= 21°C and 115 k

= 22°C. The reading is

120-118.7 = 1.3 k

above 21°C which is

1.3k

Ω ×

1

°

C

120 – 115k

= 0.26

°

C

Therefore 118.7 k

is 21.26°C.

Measurements Using the Thermal Efficiency Apparatus

Direct Measurements

Three quantities may be directly measured with the
Thermal Efficiency Apparatus: temperatures, the power
delivered to the hot reservoir, and the power dissipated by
the load resistors. The details of how these measurements
are made follow.

Temperatures

The temperatures of the hot and cold reservoirs are
determined by measuring the resistance of the thermistor
imbedded in the hot or cold block. To do this, connect an
ohmmeter to the terminals located as shown in Figure 4.
The switch toggles between the hot side and the cold side.
The thermistor reading can be converted to a temperature

461

-5

436

-4

413

-3

391

-2

370

-1

351

0

332

1

315

2

298

3

283

4

269

5

255

6

242

7

230

8

218

9

207

10

197

11

187

12

178

13

169

14

161

15

153

16

146

17

139

18

133

19

126

20

120

21

115

22

109

23

104

24

100

25

95.4

26

91.1

27

87.0

28

83.1

29

79.4

30

75.9

31

72.5

32

69.3

33

66.3

34

63.4

35

60.7

36

58.1

37

55.6

38

53.2

39

51.0

40

48.9

41

46.8

42

44.9

43

43.0

44

41.2

45

39.6

46

37.9

47

36.4

48

34.9

49

33.5

50

32.2

51

30.9

52

29.7

53

28.5

54

27.4

55

26.4

56

25.3

57

24.4

58

23.4

59

22.5

60

21.7

61

20.9

62

20.1

63

19.3

64

18.6

65

17.9

66

17.3

67

16.6

68

16.0

69

15.5

70

14.9

71

14.4

72

13.8

73

13.4

74

12.9

75

12.4

76

12.0

77

11.6

78

11.2

79

10.8

80

10.4

81

10.1

82

9.76

83

9.43

84

9.12

85

8.81

86

8.52

87

8.24

88

7.96

89

7.70

90

7.45

91

7.21

92

6.98

93

6.75

94

6.53

95

6.33

96

6.12

97

5.93

98

5.74

99

5.56

100

5.39

101

5.22

102

5.06

103

4.91

104

k

°C

k

°C

k

°C

k

°C

k

°C

Table 1: Resistance to Temperature Conversion Chart